The disclosures of these co-pending applications are incorporated herein by reference.
The following invention relates to a printhead assembly having printhead modules in a channel.
More particularly, though not exclusively, the invention relates to a printhead assembly for an A4 pagewidth drop on demand printer capable of printing up to 1600 dpi photographic quality at up to 160 pages per minute.
The overall design of a printer in which the assembly can be utilized revolves around the use of replaceable printhead modules in an array approximately 8xc2xd inches (21 cm) long. An advantage of such a system is the ability to easily remove and replace any defective modules in a printhead array. This would eliminate having to scrap an entire printhead if only one chip is defective.
A printhead module in such a printer can be comprised of a xe2x80x9cMemjetxe2x80x9d chip, being a chip having mounted thereon a vast number of thermo-actuators in micro-mechanics and micro-electromechanical systems (MEMS). Such actuators might be those as disclosed in U.S. Pat. No. 6,044,646 to the present applicant, however, might be other MEMS print chips.
In a typical embodiment, eleven xe2x80x9cMemjetxe2x80x9d tiles can butt together in a metal channel to form a complete 8xc2xd inch printhead assembly.
The printhead might typically have six ink chambers and be capable of printing four color process (CMYK) as well as infra-red ink and fixative. An air pump would supply filtered air though a seventh chamber to the printhead, which could be used to keep foreign particles away from its ink nozzles.
Each printhead module receives ink via an elastomeric extrusion that transfers the ink. Typically, the printhead assembly is suitable for printing A4 paper without the need for scanning movement of the printhead across the paper width.
The printheads themselves are modular, so printhead arrays can be configured to form printheads of arbitrary width.
Additionally, a second printhead assembly can be mounted on the opposite side of a paper feed path to enable double-sided high speed printing.
It is an object of the present invention to provide a printhead assembly having printhead modules in a channel.
It is a further object of the present invention to provide a printhead assembly having an array of printchips held into a channel wherein the channel has a coefficient of thermal expansion substantially the same as that of silicon from which the chip are primarily made.
It is a further object of the present invention to provide a method inserting individual printhead modules into a channel in forming a printhead assembly.
The present invention provides a printhead assembly for a pagewidth drop on demand ink jet printer, comprising:
a channel extending substantially across said pagewidth, and
an array of printhead modules secured to the channel so as to extend substantially across said pagewidth.
Preferably the channel is a metallic channel having a coefficient of thermal expansion substantially identical to that of a material from which the printhead modules are primarily formed.
Preferably the material from which the printhead modules are primarily formed is silicon.
Preferably the channel consists essentially of nickel iron alloy.
Preferably the channel is nickel plated.
Preferably the channel consists essentially of xe2x80x9cInvar 36xe2x80x9d.
Preferably the channel is a U-channel having walls of a selected thickness and wherein the channel is nickel plated to 0.056% of said wall thickness.
Preferably an elastomeric ink delivery extrusion extends along the channel, between a floor of the channel and the printhead modules.
Preferably walls of the channel impart force on the printhead modules so as to form a seal between ink inlets on each module and outlet holes that are formed on the elastomeric ink delivery extrusion.
Preferably the printhead modules are captured in a precise alignment relative to each other.
Preferably each printhead module has an elastomeric pad on one side thereof, the pad serving to xe2x80x9clubricatexe2x80x9d the printhead modules within the channel to take up thermal expansion tolerances without loss of alignment of the modules.
Preferably the channel is cold rolled, annealed and nickel plated.
Preferably the channel has cut-outs at each end to mate with snap-fittings on printhead location moldings.
The present invention further provides a method of assembling a printhead assembly for a pagewidth drop on demand ink jet printer, the method comprising the steps of:
(a) providing a channel to extend substantially across said pagewidth, the channel having a pair of opposed sidewalls and a base from which the sidewalls extend,
(b) applying a force to flex the sidewalls of the channel apart at a location along the channel where a printhead module is to be installed into the channel,
(c) placing a printhead module into the channel at said location,
(d) releasing the force such that the printhead module is retained by the walls of the channel,
(e) repeating steps (b) to (d) at consecutive locations spaced along the channel until all modules of the assembly have been installed in the channel.
As used herein, the term xe2x80x9cinkxe2x80x9d is intended to mean any fluid which flows through the printhead to be delivered to print media. The fluid may be one of many different colored inks, infra-red ink, a fixative or the like.